Pressure compensated watch enclosure

ABSTRACT

At the time of the casing of a watch in the back of which a diaphragm (19) is placed, an insulating and inert transparent liquid is caused to penetrate into the interior of the case by placing the whole in an enclosure under negative pressure. The air is exhausted, and the liquid in question comes to occupy the space included between the module (1) and the walls of the case. A small quantity of air contained under the diaphragm (19) expands under the effect of the negative pressure and causes this diaphragm to swell, which gives a compensating volume allowing thereafter the thermal expansion of the liquid within the case and without subjecting the walls of the latter to stresses.

This is a continuation of application Ser. No. 247,532 filed Mar. 3,1981, now abandoned.

Patents CH 608 325 and 609 828 describe electronic wrist watches, themodule of which is protected against external influences by a liquidwhich occupies the inner space of the case. The presence of a liquid inthe environment of the electronic module of a wrist watch is known toconstitute a protection against shocks, on the one hand, and againstoxidation, on the other hand. Another factor which plays a particularlyimportant part and which tends to preserve the operating qualities of anelectronic watch when the time-standard of this watch is a quartz is thefact that the liquid also constitutes a protection against the gradualpenetration of air into the interior of the capsule of the quartz.

The production of an electronic wrist watch, the module of which bathesin a liquid, poses the problem of the expansion of this liquid in caseof increase of the temperature, or more exactly, at the time of adifferential variation of the volume of the liquid relative to thevolume of the case under the effect of a temperature variation.

The object of the present invention is to provide a new solution betteradapted than the known solutions to the requirements of practice, takinginto account the specific conditions resulting from the thermalexpansion of the liquid.

To this end, the present invention has as its subject an electronicwrist watch comprising a case in at least two parts fixed to one anotherin a fluid-tight and detachable manner, and an electronic module housedin the case and bathing in a liquid, characterized in that at least oneof the said parts of the case is deformable under stress and in that thesaid liquid is, at the ambient temperature, at a lower pressure than theatmospheric pressure, thus maintaining the said case part in a deformedposition.

For casing up, a process may be applied which also forms part of theinvention and which is characterized in that the case equipped with themodule is placed in a liquid at ambient temperature and at atmosphericpressure, the two parts of the case resting one upon the other by meansof annular seats which they both present, the air is exhausted from thecase and the latter is filled with liquid, then the whole is subjectedto a temperature rise of predetermined value while forces which pressthem on their seats are exerted on the said parts of the case, afterwhich the whole is returned to the ambient temperature while the saidexternal forces are maintained.

Several embodiments of the watch according to the invention will bedescribed below, by way of example, referring to the figures of theappended drawings,

FIG. 1 is a partial axial sectional view of a first embodiment of theinvention;

FIG. 2 is a partial axial sectional view of a second embodiment of theinvention; and

FIG. 3 is a top sectional view of a portion of a third embodiment of theinvention.

The watch depicted in the drawing comprises an electronic module 1. Itis a module of the type having a display with hands which is concerned.It therefore comprises, for example, a stepping motor (not depicted)which drives a wheel-train actuating the moving parts 2 and 3respectively bearing a minute-hand 4 and an hour-hand 5. These handsmove above a dial 6 which is fixed on the module 1. The latter containsa battery (not depicted) which plays the part of a current source.Possibly, a panel may be provided for collecting solar energy. Theconstitution of this module is of a completely usual type. As a variant,the module 1 might also be replaced by a module of the digital-displaytype with liquid crystal, with luminescent diodes, with electrochromicelements, or operating according to any other system.

The case depicted in the drawing comprises a first part designated by 7,which is formed by a glass 8 and a caseband 9, and a second part 10which forms the back of the case. The caseband 9 is cemented along theperiphery of the lower face of the glass 8. It is a matter of anarrangement which permits this caseband to be made of a material such assynthetic stone, a ceramic, etc.

The back 10 includes a flat piece, preferably metallic 11 with, in itsinner face, an annular detachment 12 which serves to accommodate agasket 13 supporting a movement-holder frame 14. A maintaining ring 15,disposed between the glass 8 and the fillet 16 of the module 1, holdsthe latter in place.

Of course, the shape of the watch described is not limited to a circularshape. The watch may as well be of rectangular, square, oval,rounded-side, etc. shape.

The central part of the piece 11 presents, in its inner face, a recess17, the bottom of which is flat. Moreover, in the vicinity of theperiphery of this recess, a groove 18 may be contrived. At the time ofthe fabrication of the back, there is placed in the recess 17 a thindiaphragm 19 of plastic material which is cut out in such a way as tolie exactly flat on the bottom of the recess 17. This diaphragm iscemented along its periphery on the inner face of the back. In theembodiment depicted, the gasket 13 is made in one piece with thediaphragm 19, of which it forms the outer rim.

Thus, the watch case described comprises a composite portion whichconstitutes the back and is composed of the rigid part 10 and of thediaphragm 19 joined to the part 10 by its periphery. This diaphragm maybe of an elastically deformable material or of a flexible material.Thus, in the case where it is lying flat against the incurvated innerface of the part 10, a diaphragm 19 of flexible material can move awayfrom the inner face of the back at the time the liquid is put undernegative pressure, the mass of air occluded between the part 10 and thediaphragm then expanding as a function of the reduction of pressurewhich is imposed upon the liquid.

It will now be described how casing takes place:

The module 1, equipped with the dial and the hands, is mounted insidethe part 7 of the case, after which the back 10, equipped with thediaphragm 19 which is laid flat in the recess 17, is placed on theperiphery of the caseband 9 with interposition of the gasket 13. Thecorresponding seats of the two parts rest one upon the other. The wholeis placed in an enclosure which contains a transparent and inertinsulating liquid, e.g., glycerin, a silicone, etc. The choice of thisliquid will be determined by the properties which it must present, andwhich result from the functions it must fulfill, as will be seen below.Before the back is tightened, the enclosure which contains the liquidand the watch is closed, and the interior of this enclosure is put undernegative pressure, by means of a vacuum pump, for example. It is easilyrealized that as the pressure falls, the air contained in the innerspace of the case escapes little by little while raising the back 10slightly, so that the liquid penetrates into the case. The pressure isreduced thus to a suitable value, which may reach, for example, 20millibars, or about 15 mm Hg. Now, at this negative pressure, the airwhich remains contained between the diaphragm 19 and the piece 11, andthe mass of which is proportioned by the volume of the groove 18,expands, so that the diaphragm 19 rises and occupies part of the volumeleft free between the back 10 and the module 1.

By way of example, if the surface covered by the diaphragm 19 attains,for example, 200 mm² and if the total volume of the space betweendiaphragm and back is on the order of 1 mm³, an average rising of thediaphragm 19 attaining 25/100 mm is going to correspond to a freedvolume on the order of 50 mm³. Thus, the expansion of the air containedoriginally in the groove 18 may attain 50 times its initial volume,which corresponds to a reduction in pressure of 98% and, consequently,to an absolute pressure of 20 millibars. The watch is then practicallyunder vacuum.

The air having been entirely exhausted from the inner space of the caseby putting the enclosure under vacuum, it then suffices to re-establishthe pressure in the vacuum chamber, preferably by pressing on a valvewhich is generally provided for in the bottom or the glass. The liquidoutside the case ensures the compression of the back against thecaseband 9. The screws 20 can then be locked.

A usual round back will be locked by manipulation from the outside inthe chamber which is under vacuum, within the liquid. It will also benoted that the part ensuring the closure will not always be the back.The glass may also play this part, as in the so-called "Vacuum" watchesalready known. An exhaust-valve, of the non-return valve type, may alsobe provided for.

It is realized that in case of temperature variations, the variations involume of the liquid which fills the inner space of the case are goingto cause variations of the volume enclosed by the diaphragm 19. Thenegative pressure therefore varies slightly. A watch is obtained, theinner space of which is maintained at negative pressure but is occupiedby a liquid. These conditions ensure the maximum of reliability for anelectronic watch, especially for a quartz watch.

If need be, the groove 18 might be eliminated, the quantity of air whichremains enclosed between the back and the diaphragm 19 at the time thelatter is put in place being sufficient to ensure the expansion of thedeformable enclosure.

One may also go about it otherwise for effectuating the casing, avoidingthe use of a device allowing a high vacuum to be caused within anenclosure containing the liquid. After the two parts of the case havebeen placed inside a recipient containing the liquid, and the air hasbeen completely exhausted from the inside of the case, the whole of theliquid contained in the recipient may be heated, up to a temperature onthe order of 60° to 80° C., for example. The mass of liquid containedwithin the case is therefore going to undergo a thermal expansion, andpart of this mass is going to leave the case. During this operation,care will be taken to exert between the two parts of the case aregulated force tending to keep the case closed, while permitting theevacuation of the surplus liquid under the effect of the expansion. Forthat purpose, the two parts of the case may be placed one upon theother, and provision may be made for causing a weight or a spring to actupon the part situated above. Once the entirety of the liquid in whichthe case and the module are bathing has been brought to the requiredtemperature, it will suffice to allow cooling. The presence of theweight or of the spring which compresses the two parts of the case oneagainst the other will prevent the liquid from re-entering the case, sothat upon cooling, the negative pressure required will be set upspontaneously. The exhaustion of the air out of the case may also beensured before the heating of the enclosure, without using a vacuumpump. It suffices, indeed, to cause any fuel to burn within the closedenclosure containing the liquid in order to bind the oxygen from theair, according to the principle described in the patent CH 533 832.

Other embodiments are also possible. The deformable case part which ismaintained in the deformed state under stress, instead of beingconstituted by the diaphragm 19 and the rigid piece 11, might also beconstituted by a usual back and a small bag made of plastic materialplaced freely or fixed by any means between the back and the module, asshown in FIG. 2. In other designs, provision might be made, for example,for a deformable enclosure constituted by a rigid tube, e.g., a tube inthe shape of a circle segment, one end of which would be closed, whereasthe other end would be open, as shown in FIG. 3. A movable plug, e.g., adrop of mercury, would separate within this tube the zone constitutingthe deformable enclosure occupied by a small mass of gas and the outerportion communicating with the inner space of the case and consequentlyoccupied by the liquid which fills the case. A metallic back or a partconstituting the glass, slightly deformable under the effect of thepressure, might also constitute the case part deformable under stress,which maintains the negative pressure in the case.

In all these embodiments, the two casing processes described above areapplicable.

If the battery is housed within the module 1, the change of batterynecessitates the opening of the case, so that it is then necessary tore-establish the vacuum and, if need be, to replace the liquid lost ateach change of battery. As has been seen above, however, this operationis extremely simple to effect.

However, it has been found that it was advantageous to keep the batteryin contact with the protective liquid. Indeed, the losses due to theinfluence of the ambient atmosphere are then reduced. As a result, thewatch described ensures a longer running time of the battery than whathas been known until now. Now, batteries are already presently knownwhich can ensure a running autonomy on the order of 6 to 7 years, sothat, practically, any battery replacement can be dispensed with.

The properties which the liquid must present are principally thefollowing: it must be transparent, insulating, chemically inert, of lowvolatility. Different liquids which meet these conditions are known,besides the silicones and glycerin, already mentioned.

On the other hand, if there is reason for allowing easy and frequentchanges of batteries, it may likewise be provided for to place thebattery in a housing separated from the inner space of the case, onlythis inner space being occupied by the liquid, whereas a separate covergives access to the battery.

Finally, the realization described lends itself more particularly todesigns in which the elements of the case are solid and rigid elements,i.e., elements of synthetic stone, of ceramics, or of sintered metallicor other compositions. Indeed, the great hardness of such materials isknown to be accompanied by a very high resistance to deformation, sothat the effect of the atmospheric pressure being exerted on the casedoes not entail practically any deformation.

I claim:
 1. A watch comprising an electronic module having a displaydevice, and a casing comprising a first enclosure formed of a pluralityof rigid wall portions sealingly connected to one another and defining amain inner space of a substantially unvariable volume which is entirelysealed from the outer atmosphere, and a second enclosure at least partlycomprised of a deformable wall portion, said second enclosure definingwithin the main inner space of said first enclosure two sub-spaces, therespective volumes of which are inversely variable through deformationof said deformable wall portion, a first one of said sub-spaces beingfilled with a liquid and containing said module and display device, theother one of said sub-spaces being filled with a gas, said liquid andsaid gas being at the same pressure, said pressure being a negativepressure.
 2. A watch according to claim 1, wherein said first enclosurecomprises a back part and a case-band part, said back part is removablysecured to said case-band part, and said deformable wall portion is aflexible diaphragm located inside said back part and joinedfluid-tightly to said back part by its periphery, the said outersub-space being defined by said diaphragm and said back part.
 3. A watchaccording to claim 1, wherein said first enclosure comprises a back partand a case-band part, said back part is removably secured to saidcase-band part, and said deformable wall portion is a bag made of aflexible material joined to the back part, disposed between the latterand the module.
 4. A watch comprising an electronic module having adisplay device, and a casing comprising a first enclosure formed of aplurality of rigid wall portions sealingly connected to one another anddefining a main inner space of a substantially unvariable volume whichis entirely sealed from the outer atmosphere, and a second enclosure atleast partly comprised of a deformable wall portion, said secondenclosure defining within the main inner space of said first enclosuretwo sub-spaces, the respective volumes of which are inversely variablethrough deformation of said deformable wall portion, a first one of saidsub-spaces being filled with a liquid and containing said module anddisplay device, the other one of said sub-spaces being filled with agas, said liquid and said gas being at the same pressure, said pressurebeing a negative pressure, said deformable wall portion comprising atubular rigid element having a closed end and a plug located within saidtubular element which is spaced apart from said closed end and movablewithin said tubular element, said other sub-space being defined by saidtubular element, said plug and said closed end.